"""Input box widget for the TUI.

A multi-line prompt: ``Enter`` sends the message and long lines soft-wrap
visually (``TextArea`` defaults to ``soft_wrap=True``). The field grows with
content up to ``max-height`` and then scrolls internally.

A hard line break cannot be inserted via a modifier+Enter combo because the
common terminals do not distinguish Ctrl/Alt/Shift+Enter from plain Enter (they
all send ``\\r``), so any such binding would collide with the submit key. Soft
wrap covers the visual multiline case; revisit if a distinguishable newline key
is needed.
"""

from __future__ import annotations

from textual import events
from textual.app import ComposeResult
from textual.containers import Vertical
from textual.widgets import TextArea

from clients.terminal.tui.events import UserSubmitted
from clients.terminal.tui.widgets.command_hints import CommandHints


class _PromptInput(TextArea):
    """Multi-line text area that submits on Enter.

    ``Tab`` completes an in-progress slash command: if the input starts with
    ``/`` and has no whitespace yet, Tab replaces the text with the canonical
    name of the top matching command (plus a trailing space) and moves the
    cursor to the end. ``Enter`` submits as before.
    """

    async def _on_key(self, event: events.Key) -> None:
        # Intercept before TextArea's own _on_key, which maps "enter" -> "\n".
        if event.key == "enter":
            event.stop()
            event.prevent_default()
            self.action_submit()
            return
        if event.key == "tab" and self._complete_command():
            event.stop()
            event.prevent_default()
            return
        await super()._on_key(event)

    def _complete_command(self) -> bool:
        """If typing a slash command, complete to the top match. Returns True if handled."""
        text = self.text
        if not text.startswith("/") or any(ch.isspace() for ch in text):
            return False
        from clients.terminal.tui.commands.registry import get_registry

        matches = get_registry().match(text[1:])
        if not matches:
            return False
        self.text = f"/{matches[0].meta.name} "
        self.move_cursor((0, len(self.text)))
        return True

    def action_submit(self) -> None:
        text = self.text
        if text.strip():
            self.post_message(UserSubmitted(text))
        self.text = ""


class InputBox(Vertical):
    """Bottom prompt frame with a multi-line input field."""

    DEFAULT_CSS = """
    InputBox {
        height: auto;
        min-height: 3;
        border: heavy $tui-prompt-border;
        background: $tui-surface;
        color: $tui-text;
        padding: 0 1;
    }
    InputBox > TextArea {
        height: auto;
        min-height: 1;
        max-height: 12;
        width: 100%;
        border: none;
        background: $tui-surface;
        color: $tui-text;
        padding: 0;
    }
    InputBox > TextArea:focus {
        border: none;
        background-tint: transparent;
    }
    """

    def __init__(self) -> None:
        super().__init__()
        self._hints = CommandHints()
        self._input = _PromptInput(
            text="",
            placeholder="Ask anything... (Enter to send)",
            classes="input-field",
            show_line_numbers=False,
            soft_wrap=True,
        )

    def compose(self) -> ComposeResult:
        yield self._hints
        yield self._input

    def on_mount(self) -> None:
        self._input.focus()

    def on_text_area_changed(self, event: TextArea.Changed) -> None:
        # Only the prompt's own textarea drives the hints.
        if event.text_area is self._input:
            self._hints.update_for(self._input.text)

    def focus_input(self) -> None:
        self._input.focus()

    def set_placeholder(self, text: str) -> None:
        self._input.placeholder = text